Eddy current array (ECA) inspection is commonly used to detect flaws in surfaces of manufactured metal components such as turbine engine components. During this type of inspection, electro-magnetic induction is used to induce eddy currents in the component being inspected. A plurality of sensors inside an ECA probe separately generates alternating magnetic fields, which induces the eddy currents in the component while the probe is moved near the component. When flaws are present in the component, the flow of eddy currents is altered. The altered eddy currents produces changes in a secondary magnetic field which are detected by the array of sensors inside the ECA probe. An ECA acquisition unit monitors variations of secondary magnetic fields to produce readings for each of the ECA probe sensors which are typically representative of the flaw size. A complete scan of the dovetail is typically achieved by moving the probe along the entire dovetail length while acquiring ECA readings and position information in order to construct a cscan image representative of the actual condition of whole inspected surface of the dovetail.
The reliability and accuracy of the measurement depend on the ECA probe being properly positioned in the dovetail in order to maintain, for all inspections, a relatively constant sensor to part distance (Lift-off). Another important aspect is the ability to track the position of the probe in the dovetail slot in order to accurately reconstruct the cscan image.
Past solutions to produce a reliable cscan image from an ECA scan of a dovetail slot were not adapted for the deployment of a versatile, portable and reliable product. For example, U.S. Pat. No. 7,800,364 describes a solution where the probe manipulator itself provides a precise position reference to the probe using the adjacent dovetail slots as reference. Such a solution requires an important redesign for every dovetail design and in thus not adapted for a product with large deployment.
Other solutions provided patents such as U.S. Pat. Nos. 5,315,234, 5,442,286, 6,339,326, 6,545,467, 6,563,307 and 6,812,697 use conformable probe supports and some actuation mechanism to expand the probes and force the sensors onto the dovetail inner surfaces. In this case, one drawback is the frequent probe damage that occurs when the ECA probe moves near part edges which causes excessive strain on the probe. Another drawback is the need for automation in order to expand the probes in the dovetail slot, which typically requires the use of a robot to conduct the inspection.
Therefore there is an unmet need for a solution to provide a portable and reliable ECA probe and manipulator system easily adaptable to multiple turbine disk designs.